CN113462976A - High-fatigue-strength bolt steel, preparation method thereof and bolt manufacturing method - Google Patents
High-fatigue-strength bolt steel, preparation method thereof and bolt manufacturing method Download PDFInfo
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- C21D1/18—Hardening; Quenching with or without subsequent tempering
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Abstract
The invention discloses high-fatigue-strength bolt steel, a preparation method thereof and a bolt manufacturing method, belongs to the technical field of high-strength bolt steel, and solves the problem that the fatigue performance of a bolt cannot be improved under the condition that the strength level of the bolt is not changed in the prior art. The bolt steel comprises the following components in percentage by mass: 0.32-0.45% of C, 0.15-0.37% of Si, 0.30-0.90% of Mn, 0.90-1.30% of Cr, 0.25-0.45% of Mo, 1.0-4.0% of Ni, 1.0-1.5% of Cu, 0.5-2.0% of Al, less than or equal to 0.015% of P, less than or equal to 0.010% of S, less than or equal to 0.005% of N and the balance of Fe. The preparation method comprises the following steps: carrying out quenching and tempering heat treatment on the hot-rolled and annealed round steel to obtain a bolt blank; and (4) carrying out induction heating tempering on the bolt blank so that a hardened layer is formed on the surface of the bolt blank, and obtaining the high-fatigue-strength bolt steel. The high-fatigue-strength bolt steel, the preparation method thereof and the bolt manufacturing method can be used for manufacturing bolts.
Description
Technical Field
The invention belongs to the technical field of high-strength bolted steel, and particularly relates to high-fatigue-strength bolted steel, a preparation method of the high-fatigue-strength bolted steel and a manufacturing method of a bolt.
Background
The high-strength bolt is a basic part required by high-end equipment manufacturing industry, is widely applied to the fields of bridges, high-speed rails, wind power, automobiles and the like, along with the continuous development of the equipment manufacturing industry in the world, the performance requirement on a basic connecting fastener is continuously improved, and more severe requirements are provided for the comprehensive performance of the high-strength bolt, particularly the bolt used for connecting a tower barrel and a blade in the wind power industry, bears high-strength alternating stress fatigue load and corrosion of the atmospheric marine environment, and needs to have comprehensive performances such as fatigue resistance, corrosion resistance, hydrogen embrittlement resistance and the like.
Among the above-mentioned properties, an increase in the strength level brings about a risk of hydrogen embrittlement, and therefore, it is difficult to improve the fatigue properties of the bolt without changing the strength level of the bolt.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a high fatigue strength bolt steel, a method for manufacturing the same, and a method for manufacturing a bolt, which solve the problem that the fatigue performance of the bolt cannot be improved under the condition that the strength grade of the bolt is not changed in the prior art.
The purpose of the invention is mainly realized by the following technical scheme:
the invention provides high-fatigue-strength bolt steel which comprises the following components in percentage by mass: 0.32-0.45% of C, 0.15-0.37% of Si, 0.30-0.90% of Mn, 0.90-1.30% of Cr, 0.25-0.45% of Mo, 1.0-4.0% of Ni, 1.0-1.5% of Cu, 0.5-2.0% of Al, less than or equal to 0.015% of P, less than or equal to 0.010% of S, less than or equal to 0.005% of N and the balance of Fe.
Further, the high fatigue strength bolting steel comprises a core part and a hardening layer wrapping the core part, wherein the hardness of the hardening layer is greater than that of the core part.
Further, the thickness of the hardening layer is 1-3 mm.
Further, the microstructure of the high fatigue strength bolting steel comprises, by mass: 0.5-2.0 NiAlCu precipitated phase and 98-99.5 sorbite.
Further, the high fatigue strength bolting steel comprises the following components by mass percent: 0.35 to 0.40 percent of C, 0.20 to 0.35 percent of Si, 0.40 to 0.75 percent of Mn, 1.05 to 1.15 percent of Cr, 0.30 to 0.40 percent of Mo, 2.8 to 3.0 percent of Ni, 1.25 to 1.35 percent of Cu, 1.0 to 1.5 percent of Al, 0.005 to 0.01 percent of P, 0.002 to 0.004 percent of S, less than or equal to 0.004 percent of N, and the balance of Fe.
Further, the high fatigue strength bolting steel comprises the following components by mass percent: 0.37 to 0.39% of C, 0.25 to 0.30% of Si, 0.35 to 0.80% of Mn, 1.0 to 1.2% of Cr, 0.28 to 0.42% of Mo, 2.5 to 3.5% of Ni, 1.2 to 1.4% of Cu, 1.0 to 1.5% of Al, 0.005 to 0.01% of P, 0.001 to 0.005% of S, less than or equal to 0.004% of N, and the balance of Fe.
Further, the grain size of the high fatigue strength bolting steel is grade 10 or more.
The invention also provides a preparation method of the high-fatigue-strength bolt steel, which is used for preparing the high-fatigue-strength bolt steel and comprises the following steps:
step 1: carrying out quenching and tempering heat treatment on the hot-rolled and annealed round steel to obtain a bolt blank;
step 2: and (4) carrying out induction heating tempering on the bolt blank so that a hardened layer is formed on the surface of the bolt blank, and obtaining the high-fatigue-strength bolt steel.
Further, the hot-rolled annealed round steel can be prepared by adopting the following method:
the raw materials are sequentially subjected to smelting (electric furnace smelting or converter smelting), refining (vacuum cycle degassing refining furnace RH or vacuum refining furnace VD), casting (continuous casting or die casting), hot rolling and annealing to obtain hot-rolled annealed round steel, wherein the annealing hardness of the hot-rolled annealed round steel is less than or equal to 269 HBW.
Further, the quenching and tempering heat treatment comprises the following steps:
and sequentially carrying out quenching heat preservation, cooling (for example, water cooling or oil cooling), tempering heat preservation and cooling (for example, water cooling) on the hot-rolled annealed round steel, wherein the quenching temperature is 860-880 ℃, the quenching heat preservation time is 1-2 min/mm, the tempering temperature is 480-620 ℃, the heat preservation time is 2-3 min/mm, and the hardness of the bolt blank is 35-44 HRC.
Furthermore, the current frequency of the induction heating and tempering is 100-200 Hz (e.g., 120-140 Hz), the heating temperature is 400-500 ℃, the heating time is 2-5 s (e.g., 2-4 s), and the heating speed is 100-150 ℃/s.
The invention also provides a manufacturing method of the high-fatigue-strength bolt, which comprises the following steps:
rolling threads and surface treatment (e.g., zinc plating, nickel plating, phosphating, etc.) are performed on the high fatigue strength bolt steel to obtain a high fatigue strength bolt; wherein the high fatigue strength bolt steel is the high fatigue strength bolt steel prepared by the method.
Compared with the prior art, the invention can realize at least one of the following beneficial effects:
a) according to the high fatigue strength bolt steel provided by the invention, Ni, Al and Cu are added to form a B2 type structure intermetallic compound precipitated phase, and a hardened layer is formed on the surface of the high fatigue strength bolt steel, namely, the high fatigue strength bolt steel comprises a core part and a hardened layer wrapping the core part, the hardness of the hardened layer is greater than that of the core part, illustratively, the thickness of the hardened layer is 1-3 mm, the fatigue strength of the high fatigue strength bolt with soft core part and hard surface can be effectively improved through the hardened layer, the hardened layer can inhibit surface fatigue crack initiation, the hardness of the core part is low, crack propagation can be inhibited, and the high fatigue strength bolt can be used for high fatigue performance requirements in the fields of wind power equipment, steel structure bridges, energy traffic and the like.
b) The high-fatigue-strength bolt steel provided by the invention can meet the requirements of 10.9 and 12.9 grades, the fatigue strength is 129-170 Mpa, under the condition of not changing the bolt strength grade, compared with the existing bolt steel, the high-fatigue-strength bolt steel has the advantages that the fatigue strength is improved by 20-30%, the tensile strength can reach more than 1100MPa, the yield strength can reach more than 1000MPa, the delayed fracture stress ratio is more than or equal to 0.8, the high-fatigue-strength bolt steel has weather resistance, and the surface hardness after induction tempering is 500-600 HV.
c) According to the preparation method of the high-fatigue-strength bolt steel, provided by the invention, through quenching and tempering heat treatment, the hardness of a bolt blank can be controlled, the integral mechanical strength of the bolt steel is ensured, and through induction heating tempering, the surface of the bolt steel is further hardened.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a metallographic graph of prior austenite grains of high fatigue strength bolt steel according to a first embodiment of the present invention;
FIG. 2 is a view showing the elemental composition of a Ni, Al, Cu intermetallic compound precipitated phase after heat treatment of the high fatigue strength bolting steel according to example 1 of the present invention;
FIG. 3 is a TEM morphology of Ni, Al, Cu intermetallic compound precipitated phases after heat treatment of the high fatigue strength bolting steel according to example 1 of the present invention;
FIG. 4 is a sectional hardness distribution diagram of examples 1 to 3 of the present invention after induction tempering treatment and comparative example 1;
FIG. 5 is a graph comparing fatigue properties of bolts produced in examples 2 and 3 of the present invention with those of comparative example 1.
Detailed Description
The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form a part hereof, and which together with the embodiments of the invention serve to explain the principles of the invention.
The invention provides high-fatigue-strength bolt steel which comprises the following components in percentage by mass: 0.32-0.45% of C, 0.15-0.37% of Si, 0.30-0.90% of Mn, 0.90-1.30% of Cr, 0.25-0.45% of Mo, 1.0-4.0% of Ni, 1.0-1.5% of Cu, 0.5-2.0% of Al, less than or equal to 0.015% of P, less than or equal to 0.010% of S, less than or equal to 0.005% of N and the balance of Fe.
Compared with the prior art, the high-fatigue-strength bolt steel provided by the invention has the advantages that Ni, Al and Cu are added to form a B2 type structure intermetallic compound precipitated phase, and a hardened layer is formed on the surface of the high-fatigue-strength bolt steel, namely, the high-fatigue-strength bolt steel comprises a core part and a hardened layer wrapping the core part, the hardness of the hardened layer is greater than that of the core part, exemplarily, the thickness of the hardened layer is 1-3 mm, the fatigue strength of the high-fatigue-strength bolt with soft core part and hard surface can be effectively improved through the hardened layer, the hardened layer can inhibit surface fatigue crack initiation, the hardness of the core part is low, crack propagation can be inhibited, and the high-fatigue-strength bolt can be used for high-fatigue-performance bolts in the fields of wind power equipment, steel structure bridges, energy traffic and the like.
Meanwhile, the high-fatigue-strength bolt steel can meet the requirements of 10.9 and 12.9 grades, the fatigue strength is 129-170 MPa, under the condition that the bolt strength grade is not changed, compared with the existing bolt steel, the high-fatigue-strength bolt steel has the advantages that the fatigue strength is improved by 20-30%, the tensile strength can reach more than 1100MPa, the yield strength can reach more than 1000MPa, the delayed fracture stress ratio is more than or equal to 0.8, the high-fatigue-strength bolt steel has weather resistance, and the surface hardness is 520-600 HV after induction tempering.
Specifically, the high fatigue strength bolting steel provided by the invention has the following functions of the components:
c: the C element is utilized to improve the strength and hardenability of the steel, and the strength and the plasticity of the steel are well matched by controlling the content of the C element.
Si: the oxidation resistance and seawater corrosion resistance of the steel are improved through the Si element, and the influence of Si on the cold heading performance of the steel is avoided through the control of the content of the Si element, so that the steel can be used for preparing parts such as bolts and the like.
Mn: mn is used for improving the hardenability and the cold-working hardening rate of the steel, and the segregation of Mn elements in the solidification process of the steel is avoided by controlling the dosage, so that the adverse effect on the cold plastic deformation of the steel is reduced.
Cr: cr is utilized to improve the hardenability, wear resistance, corrosion resistance and high-temperature strength of steel; by controlling the content, the influence on the cold processing performance of the steel is avoided; in addition, Cr can reduce the decarburization tendency and can meet the requirement of the bolt steel on surface decarburization after heat treatment.
Mo: the hardenability of the steel is adjusted by using the Mo element, the sensitivity of the steel to the temper brittleness is reduced, the temper brittleness of the steel after high-temperature tempering is prevented, the tensile strength of the steel under the high-temperature tempering condition is greatly improved, and the delayed fracture resistance of the steel is also improved.
Ni: the hardenability, low-temperature toughness and weather resistance of the steel are improved by using Ni element, Ni, Cu and Al intermetallic compound precipitated phase with B2 type structure is formed with Cu and Al, the surface hardness of the steel reaches 500-600HV after induction tempering, and the fatigue strength is improved.
Cu: the capability of forming nanocluster precipitation by using Cu element in the heat treatment process to realize surface tempering hardening is utilized, Ni, Al and Cu intermetallic compound precipitation phase with a B2 type structure is formed with Ni and Al, the surface hardness of the Ni, Al and Cu intermetallic compound precipitation phase reaches 500-600HV through the hardness after induction tempering, and the fatigue strength is improved.
Al: ni, Cu and Al intermetallic compound precipitated phase forming a B2 type structure with Ni and Cu, and the surface hardness of the alloy reaches 500-600HV through the hardness after induction tempering, thereby improving the fatigue strength.
P: controlling the content of the element P in the range can avoid the element P from forming micro segregation when the molten steel is solidified, and reduce the delayed fracture sensitivity of the steel.
S: controlling the content of the S element within the range can avoid the S element and Mn from forming MnS inclusions and reduce the influence of the inclusions on the hot-working performance of the steel.
N: the content of the N element is controlled in the range, and the content of the N element is reduced to avoid forming TiN inclusions in the steel and damaging the toughness of the steel.
Through the regulation and control of components and a preparation method, the microstructure of the high-fatigue-strength bolt steel comprises the following components in percentage by mass: 0.5-2.0 NiAlCu precipitated phase and 98-99.5 sorbite. The NiAlCu precipitated phase is precipitated by heating at 400-500 ℃ in the induction heating tempering process, and the sorbite is formed after thermal refining.
In order to further adjust the comprehensive properties, such as fatigue strength, of the high fatigue strength bolting steel, the high fatigue strength bolting steel comprises the following components in percentage by mass: 0.35 to 0.40 percent of C, 0.20 to 0.35 percent of Si, 0.40 to 0.75 percent of Mn, 1.05 to 1.15 percent of Cr, 0.30 to 0.40 percent of Mo, 2.8 to 3.0 percent of Ni, 1.25 to 1.35 percent of Cu, 1.0 to 1.5 percent of Al, 0.005 to 0.01 percent of P, 0.002 to 0.004 percent of S, less than or equal to 0.004 percent of N, and the balance of Fe.
In order to further adjust the comprehensive properties of the high fatigue strength bolting steel, such as fatigue strength, the high fatigue strength bolting steel comprises the following components by mass percent: 0.37 to 0.39% of C, 0.25 to 0.30% of Si, 0.35 to 0.80% of Mn, 1.0 to 1.2% of Cr, 0.28 to 0.42% of Mo, 2.5 to 3.5% of Ni, 1.2 to 1.4% of Cu, 1.0 to 1.5% of Al, 0.005 to 0.01% of P, 0.001 to 0.005% of S, less than or equal to 0.004% of N, and the balance of Fe.
It should be noted that, in practical applications, the grain size of the high fatigue strength bolting steel will affect the delayed fracture resistance, so that the grain size of the high fatigue strength bolting steel (i.e. the austenite grain size obtained after the quenching and tempering heat treatment) is above grade 10, and the grains are fine, which is beneficial to having better delayed fracture resistance under high strength conditions.
The invention also provides a preparation method of the high-fatigue-strength bolt steel, which is used for preparing the high-fatigue-strength bolt steel and comprises the following steps:
step 1: carrying out quenching and tempering heat treatment on the hot-rolled and annealed round steel to obtain a bolt blank;
step 2: and (4) carrying out induction heating tempering on the bolt blank so that a hardened layer is formed on the surface of the bolt blank, and obtaining the high-fatigue-strength bolt steel.
Compared with the prior art, the beneficial effects of the preparation method of the high fatigue strength bolted steel provided by the invention are basically the same as those of the high fatigue strength bolted steel, and are not repeated herein.
In addition, according to the preparation method of the high-fatigue-strength bolt steel, the hardness of the bolt blank can be controlled through quenching and tempering heat treatment, the integral mechanical strength of the bolt steel is ensured, and the surface of the bolt steel is further hardened through induction heating tempering.
For hot-rolled annealed round steel, the following method can be adopted:
the raw materials are sequentially subjected to smelting (electric furnace smelting or converter smelting), refining (vacuum cycle degassing refining furnace RH or vacuum refining furnace VD), casting (continuous casting or die casting), hot rolling and annealing to obtain hot-rolled annealed round steel, and the annealing hardness of the hot-rolled annealed round steel can be controlled to be less than or equal to 269HBW for subsequent bolt processing.
In order to further regulate and control the hardness of the bolt blank, the quenching and tempering heat treatment comprises the following steps:
the method comprises the steps of sequentially carrying out quenching heat preservation, cooling (for example, water cooling or oil cooling), tempering heat preservation and cooling (for example, water cooling) on hot-rolled annealed round steel, wherein the quenching temperature is 860-880 ℃, the quenching heat preservation time is 1-2 min/mm, the tempering temperature is 480-620 ℃, and the heat preservation time is 2-3 min/mm, so that the overall hardness of a prepared bolt blank can be effectively adjusted through adjustment of various technological parameters (for example, the quenching temperature and the tempering temperature) of quenching and tempering heat treatment on the hot-rolled annealed round steel, the hardness of the bolt blank can reach 35-44 HRC, and the overall mechanical strength of the bolt blank is further improved.
In order to avoid the influence of induction heating tempering on the hardness of the core of the bolt blank, the induction heating tempering is only acted on the surface of the bolt blank to ensure that the core has better ductility and toughness and only surface hardening is carried out, in the step 2, the current frequency of the induction heating tempering is 100-200 Hz (for example, 120-140 Hz), the heating temperature is 400-500 ℃, the heating time is 2-5 s (for example, 2-4 s), and the heating speed is 100-150 ℃/s. Wherein the heating temperature is controlled to be 400-500 ℃, and the precipitation of intermetallic compounds in the temperature range can be realized by the rapid induction heating tempering of Ni, Al and Cu, so that a hardened layer can be formed; meanwhile, the heating time is controlled to be 2-5 s, the heating speed is controlled to be 100-150 ℃/s, the penetration depth of the heating temperature can be guaranteed, and the thickness of the hardening layer is further controlled.
The invention also provides a manufacturing method of the high-fatigue-strength bolt, which comprises the following steps:
rolling threads and surface treatment (e.g., zinc plating, nickel plating, phosphating, etc.) are performed on the high fatigue strength bolt steel to obtain a high fatigue strength bolt; wherein the high fatigue strength bolt steel is the high fatigue strength bolt steel prepared by the method.
Compared with the prior art, the beneficial effects of the manufacturing method of the high fatigue strength bolt provided by the invention are basically the same as those of the manufacturing method of the high fatigue strength bolt steel provided by the invention, and are not repeated herein.
3 furnaces of steel (example 1, example 2 and example 3) are co-smelted by adopting a converter and a laboratory induction furnace according to the chemical composition requirements of the table 1, 1 furnace of 42CrMo commercial steel is required to be smelted as comparative steel (comparative example 1) according to GB/T6478-2001, the chemical compositions of the examples 1-3 and the comparative example 1 are shown in the table 1, the preparation process parameters of bolt steel are shown in the table 2, and the performance test results of bolts are shown in the table 3.
TABLE 1 chemical composition% of examples 1 to 3 and comparative example 1
| C | Si | Mn | P | S | Cr | |
| Example 1 | 0.33 | 0.20 | 0.40 | 0.006 | 0.003 | 0.90 |
| Example 2 | 0.40 | 0.28 | 0.58 | 0.008 | 0.005 | 0.98 |
| Example 3 | 0.44 | 0.35 | 0.88 | 0.012 | 0.007 | 1.06 |
| Comparative example 1 | 0.41 | 0.35 | 0.78 | 0.008 | 0.005 | 0.90 |
| Mo | Ni | Al | Cu | N | Precipitated phase | |
| Example 1 | 0.29 | 1.20 | 0.80 | 1.10 | 0.003 | 0.80 |
| Example 2 | 0.38 | 2.95 | 1.35 | 1.30 | 0.004 | 1.35 |
| Example 3 | 0.43 | 3.96 | 1.87 | 1.45 | 0.004 | 1.45 |
| Comparative example 1 | 0.21 | / | / | / | 0.007 |
TABLE 2 bolt manufacturing Process parameters for examples 1-3 and comparative example 1
TABLE 3 Performance test results of examples 1-3 and comparative example 1
The grain structure of the high fatigue strength bolting steel obtained in example 1 was characterized by an electron microscope, and the results are shown in fig. 1. As can be seen from FIG. 1, the steel sample obtained in example 1 has a uniform and fine grain structure, and the grain size is not less than 10 grade. The test results of example 1 and example 2 are similar to example 1, and the specific test results are shown in Table 3.
The tensile strength and yield strength of the steels obtained in examples 1-3 and comparative example 1 were tested according to GB/T228 Metal materials Room temperature tensile test method. The test results and the calculation results are shown in the table 3, and the strength of the high fatigue strength bolt steel after heat treatment reaches the requirements of bolts of 10.9 and 12.9 grades. FIG. 2 shows an element composition diagram of a Ni, Al and Cu intermetallic compound precipitated phase of high fatigue strength bolt steel after heat treatment, FIG. 3 shows a TEM morphology diagram of the Ni, Al and Cu intermetallic compound precipitated phase of the high fatigue strength bolt steel after heat treatment, FIG. 4 shows a section hardness distribution diagram after induction heating tempering treatment, and FIG. 5 shows a fatigue performance comparison diagram of example 2 and example 3 after being processed into bolts and comparative example 1, and the result shows that a hardened layer with the hardness of 500-600HV can be obtained at a position 1-3 mm from the surface by utilizing the precipitated phase formed by Ni, Al and Cu after surface induction heating tempering treatment, which is beneficial to improving the fatigue performance.
The fatigue strength of the bolt is evaluated by a GB/T13682 metal material axial fatigue test method, the stress range of a 10.9-grade bolt fatigue test is 745-485 MPa, the stress range of a 12.9-grade bolt fatigue test is 830-600 MPa, the test results are shown in Table 3, and the fatigue performance of bolts of 10.9 and 12.9 grades manufactured by the steel is improved by 20-30% compared with that of the traditional steel (comparison material).
As can be seen from the above examples 1-3 and comparative example 1, the high fatigue strength bolt steel provided by the invention has excellent mechanical properties and fatigue properties, the structure is refined, and the fatigue strength can be improved by 20-30% after the bolt is manufactured by adopting the steel.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (10)
1. The high-fatigue-strength bolt steel is characterized by comprising the following components in percentage by mass: 0.32-0.45% of C, 0.15-0.37% of Si, 0.30-0.90% of Mn, 0.90-1.30% of Cr, 0.25-0.45% of Mo, 1.0-4.0% of Ni, 1.0-1.5% of Cu, 0.5-2.0% of Al, less than or equal to 0.015% of P, less than or equal to 0.010% of S, less than or equal to 0.005% of N and the balance of Fe.
2. The high fatigue strength bolting steel according to claim 1, comprising a core and a hardened layer surrounding said core, said hardened layer having a hardness greater than the hardness of said core.
3. The high fatigue strength bolting steel according to claim 2, wherein said hardened layer has a thickness of 1 to 3 mm.
4. The high fatigue strength bolting steel according to claim 1, wherein said microstructure of said high fatigue strength bolting steel comprises, in mass percent: 0.5-2.0 NiAlCu precipitated phase and 98-99.5 sorbite.
5. The high fatigue strength bolting steel according to claim 1, wherein said high fatigue strength bolting steel has a grain size of grade 10 or more.
6. A method for producing a high fatigue strength bolting steel, for producing a high fatigue strength bolting steel according to any of claims 1-5, comprising the steps of:
step 1: carrying out quenching and tempering heat treatment on the hot-rolled and annealed round steel to obtain a bolt blank;
step 2: and (4) carrying out induction heating tempering on the bolt blank so that a hardened layer is formed on the surface of the bolt blank, and obtaining the high-fatigue-strength bolt steel.
7. The method for producing a high fatigue strength bolting steel according to claim 6, wherein said quenching and tempering heat treatment comprises the steps of:
and sequentially carrying out quenching heat preservation, cooling, tempering heat preservation and cooling on the hot-rolled annealed round steel.
8. The method for preparing high fatigue strength bolting steel according to claim 7, characterized in that the quenching temperature is 860 to 880 ℃, the quenching holding time is 1 to 2min/mm, the tempering temperature is 480 to 620 ℃, and the holding time is 2 to 3 min/mm.
9. The method for preparing high fatigue strength bolting steel according to claim 6, wherein said induction heating tempering has a current frequency of 100-200 Hz, a heating temperature of 400-500 ℃, a heating time of 2-5 s, and a heating rate of 100-150 ℃/s.
10. A method for manufacturing a high fatigue strength bolt, comprising the steps of:
rolling threads on the high-fatigue-strength bolt steel to obtain a high-fatigue-strength bolt;
the high fatigue strength bolting steel is manufactured by the method for manufacturing high fatigue strength bolting steel according to claims 6-9.
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| JP2003183780A (en) * | 2001-12-20 | 2003-07-03 | Kobe Steel Ltd | Steel for bolt and steel structure using bolt manufactured from the same |
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| JP2003183780A (en) * | 2001-12-20 | 2003-07-03 | Kobe Steel Ltd | Steel for bolt and steel structure using bolt manufactured from the same |
| CN101243197A (en) * | 2005-10-31 | 2008-08-13 | 杰富意钢铁株式会社 | High-strength steel excellent in delayed fracture resistance characteristics and metal bolts |
| CN103820726A (en) * | 2014-03-17 | 2014-05-28 | 河南赛诺米特种设备有限公司 | Method for manufacturing bolts with relatively high fatigue strength |
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